9,399 research outputs found
Fabrication and functionalization of PCB gold electrodes suitable for DNA-based electrochemical sensing
The request of high specificity and selectivity sensors suitable for mass production is a constant demand in medical research. For applications in point-of-care diagnostics and therapy, there is a high demand for low cost and rapid sensing platforms. This paper describes the fabrication and functionalization of gold electrodes arrays for the detection of deoxyribonucleic acid (DNA) in printed circuit board (PCB) technology. The process can be implemented to produce efficiently a large number of biosensors. We report an electrolytic plating procedure to fabricate low-density gold microarrays on PCB suitable for electrochemical DNA detection in research fields such as cancer diagnostics or pharmacogenetics, where biosensors are usually targeted to detect a small number of genes. PCB technology allows producing high precision, fast and low cost microelectrodes. The surface of the microarray is functionalized with self-assembled monolayers of mercaptoundodecanoic acid or thiolated DNA. The PCB microarray is tested by cyclic voltammetry in presence of 5 mM of the redox probe K3Fe(CN6) in 0.1 M KCl. The voltammograms prove the correct immobilization of both the alkanethiol systems. The sensor is tested for detecting relevant markers for breast cancer. Results for 5 nM of the target TACSTD1 against the complementary TACSTD1 and non-complementary GRP, MYC, SCGB2A1, SCGB2A2, TOP2A probes show a remarkable detection limit of 0.05 nM and a high specificity
Detection of finite frequency photo-assisted shot noise with a resonant circuit
Photo-assisted transport through a mesoscopic conductor occurs when an
oscillatory (AC) voltage is superposed to the constant (DC) bias which is
imposed on this conductor. Of particular interest is the photo assisted shot
noise, which has been investigated theoretically and experimentally for several
types of samples. For DC biased conductors, a detection scheme for finite
frequency noise using a dissipative resonant circuit, which is inductively
coupled to the mesoscopic device, was developped recently. We argue that the
detection of the finite frequency photo-assisted shot noise can be achieved
with the same setup, despite the fact that time translational invariance is
absent here. We show that a measure of the photo-assisted shot noise can be
obtained through the charge correlator associated with the resonant circuit,
where the latter is averaged over the AC drive frequency. We test our
predictions for a point contact placed in the fractional quantum Hall effect
regime, for the case of weak backscattering. The Keldysh elements of the
photo-assisted noise correlator are computed. For simple Laughlin fractions,
the measured photo-assisted shot noise displays peaks at the frequency
corresponding to the DC bias voltage, as well as satellite peaks separated by
the AC drive frequency
Current-Mode Techniques for the Implementation of Continuous- and Discrete-Time Cellular Neural Networks
This paper presents a unified, comprehensive approach
to the design of continuous-time (CT) and discrete-time
(DT) cellular neural networks (CNN) using CMOS current-mode
analog techniques. The net input signals are currents instead
of voltages as presented in previous approaches, thus avoiding
the need for current-to-voltage dedicated interfaces in image
processing tasks with photosensor devices. Outputs may be either
currents or voltages. Cell design relies on exploitation of current
mirror properties for the efficient implementation of both linear
and nonlinear analog operators. These cells are simpler and
easier to design than those found in previously reported CT
and DT-CNN devices. Basic design issues are covered, together
with discussions on the influence of nonidealities and advanced
circuit design issues as well as design for manufacturability
considerations associated with statistical analysis. Three prototypes
have been designed for l.6-pm n-well CMOS technologies.
One is discrete-time and can be reconfigured via local logic for
noise removal, feature extraction (borders and edges), shadow
detection, hole filling, and connected component detection (CCD)
on a rectangular grid with unity neighborhood radius. The other
two prototypes are continuous-time and fixed template: one for
CCD and other for noise removal. Experimental results are given
illustrating performance of these prototypes
Discrete input equipment design study
The study to improve the reliability of the LUT system by discrete input equipment (DIE) is reported. Subjects discussed include: specifications, packaging, aircraft integrated systems, and word formats DIE. It is recommended that maximal use of advanced technology be made, particularly the "know how' developed on the Saturn project
Stochastic dynamics of a Josephson junction threshold detector
We generalize the stochastic path integral formalism by considering
Hamiltonian dynamics in the presence of general Markovian noise. Kramers'
solution of the activation rate for escape over a barrier is generalized for
non-Gaussian driving noise in both the overdamped and underdamped limit. We
apply our general results to a Josephson junction detector measuring the
electron counting statistics of a mesoscopic conductor. Activation rate
dependence on the third current cumulant includes an additional term
originating from the back-action of the measurement circuit.Comment: 5 pages, 2 figures, discussion of experiment added, typos correcte
A silicon implementation of the fly's optomotor control system
Flies are capable of stabilizing their body during free flight by using visual motion information to estimate self-rotation. We have built a hardware model of this optomotor control system in a standard CMOS VLSI process. The result is a small, low-power chip that receives input directly from the real world through on-board photoreceptors and generates motor commands in real time. The chip was tested under closed-loop conditions typically used for insect studies. The silicon system exhibited stable control sufficiently analogous to the biological system to allow for quantitative comparisons
Shot-noise-driven escape in hysteretic Josephson junctions
We have measured the influence of shot noise on hysteretic Josephson
junctions initially in macroscopic quantum tunnelling (MQT) regime. Escape
threshold current into the resistive state decreases monotonically with
increasing average current through the scattering conductor, which is another
tunnel junction. Escape is predominantly determined by excitation due to the
wide-band shot noise. This process is equivalent to thermal activation (TA)
over the barrier at temperatures up to about four times above the critical
temperature of the superconductor. The presented TA model is in excellent
agreement with the experimental results
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